There are only five reasons why solder does not flow where you want it to. Almost every book that I have read on soldering will mention three of them. All three are bogus are have very little to do with the why your solder will not flow. Few books will actually tell you the real and only real reason solder does not flow. Here are the five reasons:
1.The piece that I am soldering is dirty: almost every book starts with this. It just is not a problem. First of all I have never cleaned a piece of solder or Silver before I soldered, unless it was so dirty that I did not want to touch it. I have never in 30 years sanded or steel wooled Silver or the solder before using it. It just is not necessary. I usually just throw it into the pickle for a while and start over. I once challenged a class to go out and get the solder and the silver dirty with what ever they found. When they brought back into the shop, we flux the pieces, and solder them together without cleaning them. No problem. So being dirty is not a good reason. 2.It is not solder! Now and then a student cuts a small piece of bezel or sheet off and then mistakes it for solder. Well, duh, of course it won’t melt like solder. So this is our own fault for not keeping the solder marked with “H”s. If you get it mixed up, it is a stupid mistake, so don’t. 3.Not enough flux: I teach that with Silver solder you can never have too much flux! Of course, you can as far as just soaking your charcoal block or soldering pad, but not as far as a good solder joint. So, if you do not flux it at all, or spray it on to the metal when it is too hot and it just evaporates off, it is again, a stupid mistake. You can see if the piece is fluxed, if it is not, flux it again!
Ok, that is the three bogus ones. The only real reason that solder does not flow is
4. Not enough heat: I tell my students that if it does not solder within 60 seconds, they need to turn up the torch! It is always not enough heat, except for reason number 5. Most books never even mention this, but solder is made to melt at a specific temperature. Until it, and the metal being soldered reaches this temperature, no amount of hoping, or praying, will get it to melt. Just common sense, so turn up your torch.
I add one more reason:
5. Not getting the silver hot enough, quick enough: If you take too long to get the piece up to the soldering temperature the solder becomes oxidized (dirty) and does not want to flow. I have a 30 second rule, if the solder does not flow in 30 seconds, turn up the torch, get a bigger tip, use two torches if you have to, but get it hotter quicker, so that the solder and the piece does not get oxidized.
I believe that not getting the piece hot enough is the reason for difficulties about 95% of the time. Sterling silver solders differently than any other metal that I know of. Because it conducts heat better than any art metal that I use, it has to be heated differently than copper, brass, nickel, or gold. It conducts heat so well that the whole piece must be thoroughly heated before concentrating the heat on your solder joint. I teach that after putting on the solder, you need to start heating the piece at the farthest point away from the solder as possible.
By the way, I teach all my students to solder every solder joint with "hard" solder. It melts at about 1500 degrees Fahrenheit. This means they have to get good with the torch. All the jewelry on this web site was done by my students with only hard solder. Most were done by beginners that never knew what solder was five weeks before they finish the piece or pieces on their page. We do not "wire" things together either!
All "soft" solders will not stay polished like sterling silver. I teach that you should use nothing but hard solder, because of just that, polishing. I like to solder a piece, and polish it so that you can never see the solder joints when I am finished. This makes it looks as if it were cast. Think of it is way: to make "easy (1325)", "medium (1360)", and hard (1450), they have to add more and more "junk" metals to bring down the flow temperatures. I like hard because it polishes almost as if it was sterling and stays that way for years and years. My wife has pieces that I polished over 20 years ago, haven't touched since, and you cannot see any black oxidized solder lines.
Here is a really quick step-by-step of how I teach soldering.
1.Set the piece up on a solder surface of your choice. I like charcoal blocks for a lot of different reasons. 2.Cut some hard solder. I use only sheet solder. I cut this into large pieces compared to most silversmiths. Pieces 1/8 x1/4 inch is my average size. Sometimes I use pieces twice that size. I refuse to put several "snippets" on when I can put one large piece on. Remember, I use only hard solder. If I was using easy, I would have to use very small pieces, because of the ugly solder joints it makes. 3.Light the torch of your choice. All the jewelry on this web site was made by the students with a $18.00 torch from Ace Hardware! This is the world's worst torch to use for silversmithing, but I am extremely proud of their work, especially their first pieces. By the way, I am not the type of teacher that does the work for my students, it is all their own work. 4.Spray on Aquiflux self pickling flux. That's right, I spray it on. I was taught by an 80 year old silversmith almost 30 years ago. He had gotten quite shaky, and could not "paint" on flux without completely moving everything. Because of this, one night I tried putting flux in a spray bottle and spraying it on. It worked great, and I have used this method ever since. Of course, I have found that I did not invent the wheel. I have talked to many people who have used spray bottles for years before I did! Everything that I teach was taught to me by someone! I just have tried to use the best method for me. 5.Heat the piece only enough to dry the flux past the "crusty" stage. 6.Spray on more, and heat the piece again if it did not get completely covered with flux. I flux the whole piece every time! 7.Using bent tweezers that are spring-loaded to shut, place the solder on the joints. Use lots if you are using hard solder, almost none if you are using easy. 8.Begin heating the piece as far away from the joint as possible. I teach my students to keep the torch moving so that their reaction time is increased. They can move the torch off the piece more quickly if they are already in motion. 9.Watch for the silver to start to change color as the torch moves over it. It will start to "shimmer." This is not quite the same as the shimmer when it melts, but a color change for sure. 10.Watch for the Dixon's flux to puddle, and then melt into a "syrupy" brown thick puddle. I watch the flux more than anything else to know what temperature my silver is at. I believe it must melt and flow into this syrup stage at about 1350 to 1400 degrees. 11.When the flux does its syrupy thing, I move the torch to the joint, and at the same time, I move it up slightly away from the piece. This is how I adjust the temperature of the piece. It heats up a larger area, which I believe you need in order to solder silver. (Gold is just the opposite, I think.) 12.The split second the solder flows, get off it, and I mean off of it!! I would like to shout this. I have found that you can rarely fix anything by simply adding more heat after the solder has flowed. 13.There is no 13 (unlucky you know!). If it did not solder, ask yourself which of the five reasons was responsible, pickle your piece for about 10 minutes, take a break, eat something, or at least I do, and then come back and start with step 1.